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TS125R won't start, probably the carb

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Hello!

Last summer i bought a 1991 TS125R. Only thing i wondered about was that it wouldnt rev more than 8000 rpm (red started at 9000 rpm). i kept driving until it started backfiring. After a long time searching what was wrong i opended the cylinder and the pistonrings was burned.

I changed the piston, after that it started directly.

then i was going to start it like 2 days after, it would not even idle and was dying when you gave it throttle. It would run if you was in 1st gear in 4-5000 rpm. It only ran while using the choke.

So today i was cleaning the carb, i cleaned all the jets and i used compressed air to clean the carb.

After that i went out to start it, it was completely dead...... The only thing that worked was "start gas" as we call it in sweden. Then it started up for a few seconds.

It has compression, gets air and gas as far as i know.

It is gas in the bottom of the carb so i think its something between the jets and cylinder

Thanks in advance

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DUDE, if you are reving a TS125 to 8k regularly, you are KILLING THE MOTOR!

 

Most likely the rest of the motor, espcially the crank seals, are worn out and leaking, so you get no lower end compression.

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As far as i know the engine is pretty similar to the 1994 rm 125, which is a motocross.

I've ridden alot of motocross and i rev my ktm 150 like 13k all the time with no problem.

The ts125r isnt red-lined until 10k.

Im not revving 8k regularly, just noticed it wont rev past 8k even though its redlined at 10k.

Thanks for helping me out!

BUT, youre probably right. The gearbox-oil smells gasoline.....

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If your gear oil smells like fuel, your crank seals are done. That has a big effect on mixture, which could be why it won't rev as high as normal. It also explains the need for "start gas".

Big thanks!

It started backfiring a while ago, more and more. Then it wouldnt start after a while.

The piston was burnt, could that be the reason why the piston was burnt? Fuel in the oil cannot be good.

Edit: i also checked youtube and stuff. My bike doesnt smoke when its warm, one of the symptoms of worn crank seals?

When it ran a couple of months ago, i didnt notice any trouble starting it when it was warm. (Just ridden a couple of miles the latest months).

Also, a week ago i took a ride with it. After i accelerated (10 seconds after), it would completely die. Just dont wanna belive its the crank seals..

Edited by ktmwille

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When you say piston was burnt, do you mean black with carbon, or a hole in it? But either way, yeah the crank seals could be why.

I edited last status.

The piston rings on the exhaust side was stuck (half of the piston was black (exhaust side))

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